Hydrogen Peroxide Induced Antioxidant-Coupled Redox Regulation of Germination in Rice: Redox Metabolic, Transcriptomic and Proteomic Evidences

The present study explored the impact of H2O2-induced redox manipulation on the oxidative windows of the germinating seeds of two contrasting indica rice cultivars (Oryza sativa L., Cultivars SR26B and Ratna) in calibrating germination and seedling establishment. The salt-resistant cultivar SR26B exhibited significantly improved antioxidant-conjugated redox buffering as compared to the salt sensitive rice Ratna under both elevated and lower doses of H2O2 (20 mM & 500 mu M H2O2) by augmenting the Halliwell-Asada pathway and downregulating the oxidative damages to the juvenile tissue (assessed in terms of sensitive redox biomarkers like total ROS, H2O2, O-2(.-),free carbonyl, membrane protein thiol, total thiol content, and lipid peroxidation, radical scavenging properties). Further, low magnitude inductive pulse of H2O2 treatment (500 mu M H2O2), particularly for the salt-tolerant cultivar SR26B assist significantly in maintaining redox homeostasis by augmenting both the expression of genes of H2O2 processing enzymes (SodCc2,CatA, OsAPx2, GRase) and their activities, suggesting the central role of antioxidant-coupled redox buffering and maintenance of ROS homeostasis during germination for the salinity-resistant cultivar SR26B. Comparative proteomic approach involving 2D-MALDI TOF MS/MS revealed several deferentially expressed proteins under low titre H2O2 treatment in both the rice cultivars. Some significant deferentially expressed proteins identified by mass spectrometry, matched diverse protein species which are primarily involved in redox homeostasis, cell defence, photosynthesis and energy metabolism, etc. Overall, the result indicates a good correlation between H2O2 manipulated internal redox cues, oxidative changes and oxidative stress responsive proteins in two rice cultivars necessary for germination.